My invention relates to a temperature control circuit, and particularly to a temperature control circuit for controlling the output power of electronic equipment as an inverse function of sensed temperature.
In a majority of or almost all present-day electronic equipment, particularly radio transmitters, all of the amplifiers and power amplifiers are solid state devices or transistors. Such devices are very sensitive to heat, so that if their temperature increases, their anticipated life decreases by a factor much larger than the temperature increase factor. For example, the anticipated life of a type 2N6201 transistor is 10 million hours at a junction temperature of 100 degrees C. If this temperature is increased fifty percent to 150 degrees C, the anticipated life of the transistor is decreased by ninety percent to 1 million hours. Therefore, control of the transistor temperature is very important.
Accordingly, a primary object of my invention is to provide a new and improved circuit for controlling the temperature of a transistor.
Another object of my invention is to provide a new and improved circuit for maintaining the temperature of a transistor at a desired level.
Where transistors are used in electronic apparatus, and particularly in radio transmitters, it is desirable to keep the transistors operating at a reduced power if the transistor temperature rises.
Accordingly, another object of my invention is to provide a temperature control circuit that reduces the current supplied to a transistor in response to a temperature increase so as to keep the transistor and associated apparatus in an operating condition.
Another object of my invention is to provide a temperature control circuit that reduces the current supplied to a transistor in response to a temperature increase so as to keep the equipment utilizing the transistor in an operating condition and also to lower the temperature to increase the life of the transistor.
Another object of my invention is to provide a temperature control circuit that reduces the current supplied to a transistor in response to a temperature increase, and to increase the current supplied to the transistor back to its desired level in response to a temperature decrease.